1. Field of the Invention
The invention is directed to wellbore conditioning systems and devices. In particular, the invention is directed to systems and devices for conditioning horizontal wellbores.
2. Background of the Invention
Drill bits for drilling oil, gas, and geothermal wells, and other similar uses typically comprise a solid metal or composite matrix-type metal body having a lower cutting face region and an upper shank region for connection to the bottom hole assembly of a drill string formed of conventional jointed tubular members which are then rotated as a single unit by a rotary table or top drive drilling rig, or by a downhole motor selectively in combination with the surface equipment. Alternatively, rotary drill bits may be attached to a bottom hole assembly, including a downhole motor assembly, which is, in turn, connected to a drill string wherein the downhole motor assembly rotates the drill bit. The bit body may have one or more internal passages for introducing drilling fluid, or mud, to the cutting face of the drill bit to cool cutters provided thereon and to facilitate formation chip and formation fines removal. The sides of the drill bit typically may include a plurality of radially or laterally extending blades that have an outermost surface of a substantially constant diameter and generally parallel to the central longitudinal axis of the drill bit, commonly known as gage pads. The gage pads generally contact the wall of the borehole being drilled in order to support and provide guidance to the drill bit as it advances along a desired cutting path or trajectory.
During the drilling of horizontal oil and gas wells, for example, the trajectory of the wellbore is often uneven and erratic. The high tortuosity of a wellbore, brought about from geo-steering, directional drilling over corrections, and/or formation interaction, makes running multi stage expandable packer assembles or casing in such wells extremely difficult and sometimes impossible. While drilling long reach horizontal wells, the friction generated from the drill string and wellbore interaction severely limits the weight transfer to the drill bit, thus lowering the rate of penetration and potentially causing numerous other issues and, in a worst case scenario, the inability to reach the total planned depth of the well.
Currently the majority of hole enlargement tools have either a straight mechanical engagement or hydraulic engagement. These tools have had several reliability issues, including: premature engagement, not opening to their desired position, and not closing fully, all of which can lead to disastrous results. Such tools include expandable bits, expandable hole openers, and expandable stabilizers. The use of conventional fixed concentric stabilizers and reaming-while-drilling tools have also proven to be ineffective in most cases.